Controlling the positioning of harvesting heads relative to combines using hydraulic control systems is generally known. In these systems, the position of the head relative to the surface of the head is operating over (field) is sensed. Based upon the position, the control is configured to move the head so that the head is positioned relative to the surface at a distance equivalent to a set point distance selected by the operator of the combine. In many of the hydraulic control systems, when the harvesting head position falls outside of a range for the set point, the control provides a hydraulic signal which normally causes a jerking action at the head upon initiation and termination of head movement. To eliminate this jerking, many systems have incorporated hydraulic accumulators which dissipate the effects of jerking which occurs during motion initiation and termination.
In addition to the requirement of accumulators, another drawback with harvesting head control systems, hydraulic and electronic, is they typically do not provide the operator with the capability of controlling the maximum raising speed or the maximum lowering speed independently of each other. Depending upon the harvesting application, operator comfort and vehicle performance can be improved by permitting the operator to independently set the velocity by which the harvesting head is raised and lowered.
Accordingly, it would be desirable to provide a harvesting head position control system having independent adjustment of the raise and lowering velocities, and also provide a manner of setting the acceleration and deceleration of the harvesting head during motion initiation and termination, respectively. Furthermore, it would be desirable to provide a digital electronic system incorporating the above-referenced features to provide other control features for the harvesting head, while reducing or eliminating the need for a hydraulic accumulator.